PhD position : "Modulated Frequency Selective Surfaces for enhanced dichroic mirrors"

PhD proposal 2024

Modulated Frequency Selective Surfaces for enhanced dichroic mirrors

Background

Frequency selective surfaces (FSS) are passive periodic structures that allow to direct the energy from an impinging electromagnetic (EM) wave into different directions in space. This way, FSS can be seen conceptually as space multiplexers that drive different frequencies to different directions in space. FSS are key elements in large telecommunication gateway antennas where they operate as dichroic mirrors. In this case, they are used to direct the waves associated to different frequencies from or to feeds located at virtual focal points of the reflector [Pasian]. For telecom applications, the frequencies considered range from Ka band to Q and V bands. Current solutions allow separating two frequency bands, and they are based on 2D purely periodic architectures.

Objective and application

This thesis aims is to develop innovative FSS with enhanced multiplexing capabilities. The foreseen application is new dichroic mirrors for large telecom gateway antennas.

Fundamental challenges

1) Modulated FSS for enhanced dichroic mirrors.

With a conventional purely periodic FSS, performance is limited due to the variation of the incidence angles of the impinging waves along the mirror. Indeed, the response of the FSS elementary cell varies with the incidence angle which leads to an increase in losses and cross polarization. In the proposed thesis, Modulated FSS (MFSS) will be explored to overcome this limitation. Each cell of the MFSS will be optimized to compensate for the incidence effects. This approach is directly inspirited by reflectarray synthesis methodologies in which the partners have extensive experience [Guarriello]. The MFSS concept will be implemented by exploiting the high number of Degrees of Freedom (DoF) offered by multilayer Phoenix cell [Moustafa] to improve the amplitude and phase features, thus optimizing the response in the reflection and in the transmission bands (return losses in transmission, leakage in reflection, phase unbalance in transmission and in reflection). A large set of DoF needs to be cleverly handled to generate database to be exploited in the MFSS concept.

2) Multibeam multiplexing.

Classical periodic FSS allows to spatially discriminate two frequency bands. We aim to design MFSS allowing to separate multiple bands (“multibeam multiplexing”) by directing the associated EM signals in different directions. Similar concepts are explored in the optical domain to realize meta-lenses whose focal point depends on the color [Jung] or reflectors combining focusing and filtering functions [Sadeqi]. With this multifunctionality, a single MFSS screen could potentially perform the functions performed by two conventional FSS screens or more.

Technological challenge

The frequency increase towards the mm bands is also an axis of the proposed thesis. The manufacturing technologies usually used in microwave bands will encounter limitations and technologies inherited from microelectronics will be considered. We aim to increase our competence in this field to develop a national know-how. We wish to explore available techniques such as screen printing, electrolytic growth or substrate machining.

The research team: Institut d’Electronique et des Technologies du numéRique (IETR) & Thales Alenia Space France (TASF)

The design of MFSS will combine the problems of FSS synthesis and modulated quasi-periodic surfaces. TASF and IETR have extensive experience in these fields with numerous significant scientific contributions in the design of cells [Moustafa], full-metal dichroic mirrors [Legay] or optimization of quasi-periodic surfaces [Guarriello].

Regarding the fabrication, we will work in collaboration with the NanoRennes platform involving IETR and Institut FOTON, with micro-fabrication capabilities.

For the characterization of the prototypes, we will rely on the IETR unique experimental platform.

Dates, locations and PhD supervision

• Starting date: October 2024.
• Duration: 36 months.
• Full 3 years scholarship provided (gross salary of at least 2100 Euros / month).
• Locations: IETR Rennes, France (50%) and Thales Alenia Space Toulouse, France (50%), the lengths of the two periods will be adjusted according to the research progress and the wishes of the doctoral student.
• PhD director: Renaud LOISON (IETR).
• Co-supervision: Erwan FOURN (IETR) and Andrea Guarriello (TASF).

Profile and application

• Profile: student in last year of master's degree or final year of engineering training in electronics and/or telecommunications.
• Citizenship: European Union or Switzerland.
• Apply by email to:
  • Renaud.Loison@insa-rennes.fr
  • Erwan.Fourn@insa-rennes.fr
  • Andrea.Guarriello@thalesaleniaspace.com
• Send: resume + motivation letter + transcripts (bachelor, first year of master’s degree) + reference letter(s) if possible (pdf format for all documents).

Bibliography

[Pasian] M. Pasian et al., “Multiphysics design and experimental verification of a quad-band dichroic mirror for deep space ground stations”, IET Microwaves, Antennas & Propagation, 7(6):391–398, 2013.

[Jung] J. Jung et al., "Broadband metamaterials and metasurfaces: a review from the perspectives of materials and devices" Nanophotonics, 2020.

[Sadeqi] A. Sadeqi et al., "Three dimensional printing of metamaterial embedded geometrical optics (MEGO)” Microsyst Nanoeng , 2019.

[Moustafa] L. Moustafa et al, "The Phoenix Cell: A New Reflectarray Cell With Large Bandwidth and Rebirth Capabilities," in IEEE Antennas and Wireless Propagation Letters, vol. 10, pp. 71-74, 2011.

[Legay] H. Legay et al, “Ecran dichroïque métallique”, Brevet déposé le 14/04/2022, FR2203458.

[Guarriello] A. Guarriello et al., "Structural and Radio Frequency Co-Design and Optimization of Large Deployable Reflectarrays for Space Missions", in IEEE Transactions on Antennas and Propagation, vol. 71, no. 5, pp. 3916-3927, May 2023.